Can't get boat up over 3200rpms

[rcmeyer]

Bought a 1991 26ft Regal that had been sitting indoors for about 1.5 years. It has a 454 7.4L MerCruiser. Before I ran it I replaced both batteries, changed the oil and filled it up w gas from the marina. Ran good first two times I took it out. Third time it ran good for about 45 mins then the rpm's slowly started to drop. Wouldn't go over 3200. I'd get on the throttle and it was trying but just wouldn't. It didn't stall or anything. We've replaced plugs, ignition control module, rotor cap and distributor. Temp, volts and pressure are all fine. Someone mentioned water in the fuel but wouldn't I notice that at even 2000 or 2500 rpms? What about the carb? Could the air/fuel mixture not be right? I want to exhaust all options before I start having someone tear into the engine. Also, after I've let it sit for a few hours I can get it up to about 4100 to get it up on plane. But then 5 mins later...rpm's drop back down to 3000

Any feedback would help.

Thanks,

Ryan

 

[jtmarten]

Re: Can't get boat up over 3200rpms

Fuel pump, fuel lines collapsed/partially plugged, fuel tank vent bad, bad coil, fuel filter; just a few of the potential troublemakers.

 

[Bondo]

Re: Can't get boat up over 3200rpms

Ayuh,... Ya otta start with the fuel Filters... Look for Water...

 

[JustJason]

Re: Can't get boat up over 3200rpms

What part of SW Florida? I'm moving myself down there in a month.

As with that the other 2 guys said. Start with your boat side fuel system. You can read all about a nifty test I wrote in the "adults only"section.

 

[rcmeyer]

Re: Can't get boat up over 3200rpms

If it were an issue with the fuel wouldn't it effect the boat no matter what rpm's i was at? For instance, if there were collapsed fuel lines wouldn't start acting up at 2000 rpms?

I live in Ft Myers Florida. I've been here 6 years and I love it. Great boating!

Thanks

 

[JustJason]

Re: Can't get boat up over 3200rpms

http://forums.iboats.com/showthread.php?t=283269

Give that thread a read, thats the boat fuel system test. I do this by trade, and before I dig into a carb I always give a quick check to the ignition system, do the boat side fuel test, if those both pass then I know it's a dirty carb.
I always always always do it that way so I never make a mistake and end up rebuilding a carb for free. Besides... I've seen to many a boat up here in New England that has a little to much yankee engineering, and it's very common to have more than 1 problem the older a boat gets.

Air leaks into fuel lines will cause intermitent fuel supply problems. Fuel pumps that are 1/2 buggered up can cause intermittent fuel supply problems (especially on older boats with steel tanks) And of course if you have junk floating in the carb, fuel supply to the motor will be intermitent (and usually only get worse).

I'll be in cape coral in 4 to 6 weeks if you need a mechanic. I'm actually here right now and hoping to get my rental deal closed tomorrow, and out on thursday to tie up some odds and ends, finnish a few jobs for customers that have been calling me from up north, and get me and the Ms packed. I'm closing out on Massachusettes after 7 years, I've had enough of the 6 months on, 6 off work schedule.
If you would like my work email or ## feel free to PM me.
JJ

 

[John_S]

Re: Can't get boat up over 3200rpms

I'll be in cape coral in 4 to 6 weeks if you need a mechanic. I'm actually here right now and hoping to get my rental deal closed tomorrow, and out on thursday to tie up some odds and ends, finnish a few jobs for customers that have been calling me from up north, and get me and the Ms packed. I'm closing out on Massachusettes after 7 years, I've had enough of the 6 months on, 6 off work schedule.
If you would like my work email or ## feel free to PM me.
JJ

Just like to say, good luck on your move, Jason. I am sure you will build up a faithful clientel in very short order.

As far as us yankee hacks, it's that 6 months of non-boating that drives up up a wall!

 

[JustJason]

Re: Can't get boat up over 3200rpms

Haha. Thanks John!

BTW... I specifically said "engineering" and not hacks I try to stay somewhat pc.

Last bit of fun yankee engineering I saw was actually on the last boat I worked on before I left.
The fuel line was some sort of hydraulic line with crimped on threaded ends... Something you'd see on a forklift. What the PO did was remove the fuel filter housing, installed the line on the tank side, run it under the engine, and then screwed the filter housing on to it, then rebolted the filter housing down.

I just decided to cut it in half to get it out, that and I wanted to see what the inside of it looked like. If anybody wants to know... ethonal fuel will collapse a hydraulic high pressure line